1. Field of the Invention
The present invention relates generally to circuit breakers and, more particularly, to an improved arc chute for a circuit breaker. Specifically, the invention is related to an arc chute having arc plates that are mounted in grooves formed in the arc chute wrapper.
2. Description of the Related Art
Numerous types of circuit breakers are known and understood in the relevant art. One of the purposes for which circuit breakers are provided is to interrupt an electrical circuit on command or according to certain criteria. Circuit breakers thus typically include a set of stationary electrical contacts and a set of moveable electrical contacts. The stationary and moveable contacts are in physical contact with one another when it is desired that the circuit breaker provide electricity therethrough to a load. When it is desired to interrupt the circuit, however, the moveable contacts are moved away from the stationary contacts, thus removing the moveable contacts from physical contact with the stationary contacts, creating a space therebetween, and interrupting the circuit.
As is understood in the relevant art, however, the movement of the moveable contacts away from the stationary contacts results in the formation of an electrical arc in the space between the moveable and stationary contacts beginning at the time the moveable and stationary contacts are initially separated. Such an arc is undesirable for a number of reasons. For example, the arc evidences current flowing through the circuit breaker to the load when it is desired that no such current should flow thereto. Additionally, an arc extending between the stationary and moveable contacts often results in vaporization or sublimation of the contact material itself, eventually resulting in destruction or pitting of the moveable and stationary contacts. It is thus desired to eliminate any such arcs as soon as possible upon their propagation.
As is understood in the relevant art, the moveable contacts typically are mounted on pivoting arms that pivot the moveable contacts away from the stationary contacts. An arc chute is provided along the path of each arm to break up and dissipate such arcs. Such arc chutes typically include a plurality of spaced apart arc plates mounted in a wrapper, the arc plates being aligned with the axis about which the arm pivots. As the moveable contact is moved away from the stationary contact, the moveable contact moves past the ends of the arc plates, with the arc being magnetically urged toward and between the arc plates. The arc plates are electrically insulated from one another such that the arc is broken up and extinguished by the arc plates.
Such arc chutes are not, however, without limitation. For instance, arc chutes of the type known and understood in the relevant art have heretofore been manufactured using arc plates formed with spinning tabs extending outwardly therefrom and extending through holes formed in the wrapper. Such spinning tabs and holes are indicated generally at the numerals 27A and 47A, respectively, in FIG. 6 of U.S. Pat. No. 4,963,849 to Kowalczyk et al. The spinning tabs are then compressed to retain the arc plates in fixed relation to the wrapper. The outer surface of the wrapper is then coated with a layer of ceramic paint to eliminate shorts between the compressed spinning tabs of adjacent arc plates. Such shorting can occur when an arc travels through a hole formed in the wrapper to the exterior of the wrapper and thence to another arc plate or to the circuit breaker housing. The aforementioned manufacturing process is less than fully reliable in eliminating shorts.
It is thus desired to provide an arc chute wrapper that overcomes the problems of arc chute wrappers heretofore known in the art and that is relatively simple and inexpensive to manufacture.